The Thermus thermophilus HB27 genome is provided in 2 pieces of sequence (
AE017221, AE017222
) representing a total of 2210 transcripts. These sequences have been analized for their GC content as this is an important parameter for probe design.
The average GC content of these coding sequences is 69%, with a minimum and a maximum of 45% and 79% respectively. Ninety percent of these sequences have a GC content comprised between 63%and 74%. These values have been used to set OligoArray options during design. Here is the parameter set used for this particular design.

This database contains 6036 oligonucleotides to represent the Thermus thermophilus HB27
transcriptome. Among these 6036 oligonucleotides, 3818 are considered
to be fully specific to their targets according to the design parameters described
above. In other terms, this database provides oligonucleotides for
2183 transcripts and 1752 (79% of all sequences)
have at least one specific oligo representing them. The figure below gives details on the number of CDS with specific probes.

Understanding this graph: In the best case, you want the proportion of black and red genes to be as small as possible. Black ones are the genes with no probe at all. These genes will always be missing on your array. Red ones are the sequences for which OligoArray was not able to find a specific probes. However, it reported a non-specific probe. Our thresholds to define specific probes are quite conservative and many non-specific probes will actually prove to be specific in a real experiment. All other genes (blue, yellow and green) have at least one specific probe. While the number of genes with 3 specific probes may vary greatly from an organism to another, this may have little effect on your microarray design. Indeed, many will prefer to have one probe per gene, this probe being replicated several times on the array rather than having several probes per gene with less replicates.